Device with n-type semiconductor

ABSTRACT

An electronic device includes a semiconductor layer in contact with a number of electrodes, wherein the semiconductive layer includes a compound wherein either or both of the following geometric isomers of the compound are present:  
                 
wherein: n is 1, 2 or 3 for the polycyclic moiety; and 
         R 1  and R 2  are independently selected from the group consisting of a hydrocarbon ring and a heterocyclic group, wherein R 1  and R 2  are the same or different hydrocarbon ring, the same or different heterocyclic group, or one of R 1  and R 2  is the hydrocarbon ring and the other the heterocyclic group.

BACKGROUND OF THE INVENTION

Thin film transistor (referred herein as “TFT”) is the key component ofintegrated circuits for electronic devices. Although organic materialbased TFTs generally provide lower performance characteristics thantheir conventional silicon counterparts, such as silicon crystal orpolysilicon TFTs, they are nonetheless sufficiently useful forapplications in areas where high mobility is not required. These includelarge area devices, such as image sensors, active matrix liquid crystaldisplays and low-end microelectronics such as smart cards and RFID tags.TFTs fabricated from organic or polymer materials are potentially verylow cost, and may also be functionally and structurally more desirablethan conventional silicon technology in the aforementioned areas in thatthey may offer mechanical durability, structural flexibility, compactand light weight characteristics, and the potential of being able to beincorporated directly onto the active media of the devices, thuslowering manufacturing cost and enhancing device compactness fortransportability.

Currently, the most developed organic TFTs are based on pentacene andoligo or polythiophenes. The performance of these materials, in terms ofmobility and current on/off ratio, now match the requirements fornumerous applications such as active matrix addressing arrays fordisplays or basic switching and memory devices. However, most of thecompounds with the desirable properties are p-type, meaning thatnegative gate voltages, relative to the source voltage, are applied toinduce positive charges (hole) in the channel region of the devices.However, both p-type and n-type semiconductor materials are required toform a complementary circuit. Advantages of complementary circuits,compared to ordinary TFT circuits, include higher energy efficiency,longer lifetime, and better tolerance of noise.

Only a limited number of materials have been developed for the n-typecomponent of such organic complementary circuits, because of the lack ofsuitable n-type organic materials and theoretical arguments whichpredict a reduced stability of the n-conducting radical anions underambient conditions. There is a need, which the present inventionaddresses, for inventions that expand the choice of n-type semiconductormaterials suitable for electronic devices.

The following documents may be relevant:

Amit Babel et al., “Electron Transport in Thin-Film Transistors from ann-Type Conjugated Polymer,” Adv. Mater. 14, No. 5, pp. 371-374 (Mar. 4,2002), which discloses a field effect transistor made from a ladderpoly(benzobisimidazobenzophenanthroline) (“BBL”) thin film where thestructural formula of BBL is depicted in FIG. 1.

H. E. Katz et al., “A soluble and air-stable organic semiconductor withhigh electron mobility,” Nature, Vol. 404, pp. 478-480 (Mar. 30, 2000).

Patrick R. L. Malenfant et al., “N-type organic thin-film transistorwith high field-effect mobility based on aN,N′-dialkyl-3,4,9,10-perylene tetracarboxylic diimide derivative,”Applied Physics Letters, Vol. 80, No. 14, pp. 2517-2519 (Apr. 8, 2002).

Howard E. Katz et al., “Naphthalenetetracarboxylic Diimide-Basedn-Channel Transistor Semiconductors: Structural Variation andThiol-Enhanced Gold Contacts,” J. Am. Chem. Soc., Vol. 122, pp.7787-7792 (2000).

J. H. Schon et al., “Perylene: A promising organic field-effecttransistor material,” Applied Physics Letters, Vol. 77, No. 23, pp.3776-3778 (Dec. 4, 2000).

Katz et al., U.S. Pat. No. 6,387,727 B1.

Dimitrakopoulos et al., U.S. Patent Application Publication No. US2002/0164835 A1.

Hor et al., U.S. Pat. No. 4,587,189.

Hor et al., U.S. Pat. No. 5,225,307.

BRIEF SUMMARY

The present invention is accomplished in embodiments by providing anelectronic device comprising a semiconductor layer in contact with anumber of electrodes, wherein the semiconductive layer includes acompound wherein either or both of the following geometric isomers ofthe compound are present:

wherein:

n is 1, 2 or 3 for the polycyclic moiety; and

R₁ and R₂ are independently selected from the group consisting of ahydrocarbon ring and a heterocyclic group, wherein R₁ and R₂ are thesame or different hydrocarbon ring, the same or different heterocyclicgroup, or one of R₁ and R₂ is the hydrocarbon ring and the other theheterocyclic group.

There is further provided in embodiments, a thin film transistor devicecomprising:

an insulating layer;

a gate electrode;

a semiconductor layer;

a source electrode; and

a drain electrode,

wherein the insulating layer, the gate electrode, the semiconductorlayer, the source electrode, and the drain electrode are in any sequenceas long as the gate electrode and the semiconductor layer both contactthe insulating layer, and the source electrode and the drain electrodeboth contact the semiconductor layer, wherein the semiconductor layerincludes a compound wherein either or both of the following geometricisomers of the compound are present:

wherein:

n is 1, 2 or 3 for the polycyclic moiety; and

R₁ and R₂ are independently selected from the group consisting of ahydrocarbon ring and a heterocyclic group, wherein R₁ and R₂ are thesame or different hydrocarbon ring, the same or different heterocyclicgroup, or one of R₁ and R₂ is the hydrocarbon ring and the other theheterocyclic group.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects of the present invention will become apparent as thefollowing description proceeds and upon reference to the Figures whichrepresent illustrative embodiments:

FIG. 1 represents a first embodiment of the present invention in theform of a thin film transistor;

FIG. 2 represents a second embodiment of the present invention in theform of a thin film transistor;

FIG. 3 represents a third embodiment of the present invention in theform of a thin film transistor; and

FIG. 4 represents a fourth embodiment of the present invention in theform of a thin film transistor.

Unless otherwise noted, the same reference numeral in different Figuresrefers to the same or similar feature.

DETAILED DESCRIPTION

A semiconductor layer of the present electronic device contains acompound (“Compound”), wherein either or both of the following geometricisomers of the Compound are present:

wherein:

n is 1, 2 or 3 for the polycyclic moiety, particularly where n is 1 or2, when n is 2 or 3, or when n is 2; and

R₁ and R₂ are independently selected from the group consisting of ahydrocarbon ring and a heterocyclic group, wherein R₁ and R₂ are thesame or different hydrocarbon ring, the same or different heterocyclicgroup, or one of R₁ and R₂ is the hydrocarbon ring and the other theheterocyclic group.

Both geometric isomers of the compound when employed in a semiconductorlayer of an electronic device are considered n-type semiconductormaterials. The semiconductor layer in embodiments is composed solely ofeither or both geometric isomers of the compound. In other embodiments,the semiconductor layer is composed of either or both geometric isomersof the Compound and further includes one or more other materials such asa different n-type semiconductor material where any suitable ratio byweight of the various components may be employed such as from about10%(Compound)/90%(other material(s)) to about 90%(Compound)/10%(othermaterial(s)).

The term “polycyclic moiety” encompasses both unsubstituted andsubstituted embodiments. In substituted embodiments of the polycyclicmoiety, there is substitution by a substituent a number of times such asone, two, three or more times, where the substituent may be for examplea halogen, a hydrocarbon group or a heteroatom containing group. Wheretwo or more substituents are present on the polycyclic moiety, eachsubstituent may be the same or different from each other. The one ormore substituents on the polycyclic moiety may be placed at any suitableposition or positions; in other words, any suitable substitution patternmay be employed. For example, a single substituent on the polycyclicmoiety may be at position 1, 2, 3, or 4 where the position numbers aredepicted as follows.

Two substituents on the polycyclic moiety may be for instance atpositions 1 and 2, positions 1 and 3, positions 2 and 4, positions 2 and3, or positions 1 and 4 where the position numbers are depicted above.

The halogen substituent on the polycyclic moiety may be bromine,fluorine, chlorine, and iodine.

As a substituent, the hydrocarbon group on the polycyclic moiety may befor example the following:

(a) an alkyl group which may be straight chain or branched, having forinstance 1 to about 16 carbon atoms, such as methyl, ethyl, propyl,2-methylpropyl, and the like; and

(b) a phenyl group.

As a substituent, the heteroatom containing group on the polycyclicmoiety may be for example the following:

(a) an alkyloxy group having for instance 2 to about 16 carbon andoxygen atoms, particularly 2 to about 10 carbon and oxygen atoms, suchas methoxy, ethoxy, butoxy and the like.;

(b) an amino group, —N(R₃)(R₄), where R₃ and R₄ may be the same ordifferent from each other and may be for example hydrogen, an alkylgroup or an aryl group having 1 to about 10 carbon atoms, such as —NH₂,—N(CH₃)₂, —N(C₆H₅)₂, and the like;

(c) a nitro group (NO₂); and

(d) a cyano group (CN).

To illustrate the polycyclic moiety where n is 1, 2, and 3, thefollowing exemplary geometric isomers of the compound are provided:

where n is 1;

where n is 2; and

where n is 3.

When R₁ and/or R₂ is a hydrocarbon ring, the phrase hydrocarbon ringencompasses both unsubstituted and substituted embodiments. Inunsubstituted embodiments, the hydrocarbon ring may include one, two,three or more rings and may contain for instance 3 to about 30 carbonatoms, where the hydrocarbon ring may be for example the following:

(a) a benzo ring;

(b) a naphthalenediyl ring; and

(c) an alicyclic hydrocarbon which may be saturated or unsaturated andincludes for instance 3 to about 20 carbon atoms, where exemplaryalicyclic hydrocarbons are for example cyclopropylene,3-methylcyclobutylene, and 2,4-cyclopentadienylene.

When R₁ and/or R₂ is a heterocyclic group, the phrase heterocyclic groupencompasses both unsubstituted and substituted embodiments. Inunsubstituted embodiments, the heterocyclic group may include one, two,three or more rings, where one, two, three or more of the same ordifferent heteroatom may be present in the ring or rings, and theheteroatom(s) can be for instance N, O, S, P, and Se. In unsubstitutedembodiments, the heterocyclic group may contain for instance 3 to about20 atoms (referring to number of carbon atoms and heteroatom(s)) and maybe for example the following:

a pyrido;

a thieno;

a furo; and

a pyrro.

There is now a discussion when R₁ and/or R₂ are selected from among asubstituted hydrocarbon ring and a substituted heterocyclic group. Insubstituted embodiments of the hydrocarbon ring and in substitutedembodiments of the heterocyclic group, there is substitution by a ringsubstituent a number of times such as one, two, three or more times,where the ring substituent(s) can be for example an alkyl group, analkyloxy group, a halogen, and a nitrogen containing group. Where two ormore ring substituents are present, each ring substituent may be thesame or different from each other. The one, two or more ringsubstituents may be placed at any suitable position or positions; inother words, any suitable substitution pattern may be employed.

The alkyl group (ring substituent) may be straight chain or branched,having for instance 1 to about 10 carbon atoms, such as methyl, ethyl,propyl, 2-methylpropyl, and the like.

The alkyloxy group (ring substituent) may have for instance 2 to about16 carbon and oxygen atoms, particularly 2 to about 10 carbon and oxygenatoms, such as methoxy, ethoxy, butoxy, and the like.

The halogen (ring substituent) may be bromine, fluorine, chlorine, andiodine.

The nitrogen containing group (ring substituent) may be for instance thefollowing:

(a) an amino group, —N(R₃)(R₄), where R₃ and R₄ may be the same ordifferent from each other and may be for example hydrogen, an alkylgroup or an aryl group having 1 to about 10 carbon atoms, such as —NH₂,—N(CH₃)₂, —N(C₆H₅)₂, and the like;

(b) a nitro group (NO₂); and

(c) a cyano group (CN).

In embodiments of the present invention, there is provided the followingexemplary geometric isomers of the Compound:

where n is 1 as follows,

where n is 2 as follows,

where n is 3 as follows,

As an illustration, when the polycyclic moiety is unsubstituted, n is 2,and R₁ and R₂ are unsubstituted benzo groups, the Compound isbenzimidazole perylenetetracarboxylic acid diimide (referred herein as“BZP”) as depicted in Formula (12). Procedures for synthesizing BZP areknown and BZP is commercially available. An exemplary procedure forpreparing BZP is discussed in Example 1 herein.

As illustrated in Scheme 1 (where R is depicted since R₁ and R₂ are thesame), the Compounds can be generally prepared by the condensationreaction of the appropriate tetracarboxylic acid or the correspondinganhydrides with appropriate amine(s) in a solvent such as quinoline, inthe presence of a catalyst, and with heating at elevated temperaturessuch as 180 degrees C. to 230 degrees C. When R₁ and R₂ are different,two-step condensastion of tetracarboxylic acid or the correspondinganhydrides with the appropriate amine may be used.

Either or both of the cis and trans forms of the Compound may be used.If a mixture of the two geometric isomers is used, any appropriate ratioby weight may be employed such as from about 5%(cis)/95%(trans) to about95%(cis)/5%(trans). If it is desired to use only one geometric isomer,or a mixture with one geometric isomer as the main fraction, anysuitable separation and purification techniques may be employed toisolate the desired geometric isomer from the other geometric isomer.Methods such as column chromatography and vacuum sublimation may beused.

Any suitable technique may be used to form the semiconductor layercontaining the geometric isomer(s) of the Compound. In embodiments,deposition by a rapid sublimation method may be used. One such method isto apply a vacuum of about 10⁻⁵ to 10⁻⁷ torr to a chamber containing asubstrate and a source vessel that holds the Compound in powdered form.Heat the vessel until the Compound sublimes onto the substrate. Thecharge carrier mobility of such films can be capable of manipulating bycarefully controlling the heating rate, the maximum source temperatureand/or substrate temperature during process. In addition, depositioninto a film by solution deposition may be used. The phrase “solutiondeposition” refers to any liquid composition compatible depositiontechnique such as spin coating, blade coating, rod coating, screenprinting, ink jet printing, stamping and the like.

In embodiments, the present invention may be used whenever there is aneed for a semiconductor layer in an electronic device. The phrase“electronic device” refers to micro- and nano-electronic devices suchas, for example, micro- and nano-sized transistors and diodes.Illustrative transistors include for instance thin film transistors,particularly organic field effect transistors.

In FIG. 1, there is schematically illustrated a thin film transistor(“TFT”) configuration 10 comprised of a substrate 16, in contacttherewith a metal contact 18 (gate electrode) and a layer of aninsulating layer 14 on top of which two metal contacts, source electrode20 and drain electrode 22, are deposited. Over and between the metalcontacts 20 and 22 is an organic semiconductor layer 12 as illustratedherein.

FIG. 2 schematically illustrates another TFT configuration 30 comprisedof a substrate 36, a gate electrode 38, a source electrode 40 and adrain electrode 42, an insulating layer 34, and an organic semiconductorlayer 32.

FIG. 3 schematically illustrates a further TFT configuration 50comprised of a heavily n-doped silicon wafer 56 which acts as both asubstrate and a gate electrode, a thermally grown silicon oxideinsulating layer 54, and an organic semiconductor layer 52, on top ofwhich are deposited a source electrode 60 and a drain electrode 62.

FIG. 4 schematically illustrates an additional TFT configuration 70comprised of substrate 76, a gate electrode 78, a source electrode 80, adrain electrode 82, an organic semiconductor layer 72, and an insulatinglayer 74.

The composition and formation of the semiconductor layer are describedherein.

The substrate may be composed of for instance silicon, glass plate,plastic film or sheet. For structurally flexible devices, plasticsubstrate, such as for example polyester, polycarbonate, polyimidesheets and the like may be preferred. The thickness of the substrate maybe from amount 10 micrometers to over 10 millimeters with an exemplarythickness being from about 50 to about 100 micrometers, especially for aflexible plastic substrate and from about 1 to about 10 millimeters fora rigid substrate such as glass or silicon.

The compositions of the gate electrode, the source electrode, and thedrain electrode are now discussed. The gate electrode can be a thinmetal film, a conducting polymer film, a conducting film made fromconducting ink or paste or the substrate itself, for example heavilydoped silicon. Examples of gate electrode materials include but are notrestricted to aluminum, gold, chromium, indium tin oxide, conductingpolymers such as polystyrene sulfonate-dopedpoly(3,4-ethylenedioxythiophene) (PSS-PEDOT), conducting ink/pastecomprised of carbon black/graphite or colloidal silver dispersion inpolymer binders, such as ELECTRODAG™ available from Acheson ColloidsCompany. The gate electrode layer can be prepared by vacuum evaporation,sputtering of metals or conductive metal oxides, coating from conductingpolymer solutions or conducting inks by spin coating, casting orprinting. The thickness of the gate electrode layer ranges for examplefrom about 10 to about 200 nanometers for metal films and in the rangeof about 1 to about 10 micrometers for polymer conductors. The sourceand drain electrode layers can be fabricated from materials whichprovide a low resistance ohmic contact to the semiconductor layer.Typical materials suitable for use as source and drain electrodesinclude those of the gate electrode materials such as gold, nickel,aluminum, platinum, conducting polymers and conducting inks. Typicalthicknesses of source and drain electrodes are about, for example, fromabout 40 nanometers to about 1 micrometer with the more specificthickness being about 100 to about 400 nanometers.

The insulating layer generally can be an inorganic material film or anorganic polymer film. Illustrative examples of inorganic materialssuitable as the insulating layer include silicon oxide, silicon nitride,aluminum oxide, barium titanate, barium zirconium titanate and the like;illustrative examples of organic polymers for the insulating layerinclude polyesters, polycarbonates, poly(vinyl phenol), polyimides,polystyrene, poly(methacrylate)s, poly(acrylate)s, epoxy resin and thelike. The thickness of the insulating layer is, for example from about10 nanometers to about 500 nanometers depending on the dielectricconstant of the dielectric material used. An exemplary thickness of theinsulating layer is from about 100 nanometers to about 500 nanometers.The insulating layer may have a conductivity that is for example lessthan about 10⁻¹² S/cm.

The insulating layer, the gate electrode, the semiconductor layer, thesource electrode, and the drain electrode are formed in any sequence aslong as the gate electrode and the semiconductor layer both contact theinsulating layer, and the source electrode and the drain electrode bothcontact the semiconductor layer. The phrase “in any sequence” includessequential and simultaneous formation. For example, the source electrodeand the drain electrode can be formed simultaneously or sequentially.The composition, fabrication, and operation of field effect transistorsare described in Bao et al., U.S. Pat. No. 6,107,117, the disclosure ofwhich is totally incorporated herein by reference.

The semiconductor layer has a thickness ranging for example from about10 nanometers to about 1 micrometer, or from about 30 to about 150nanometers. The TFT devices contain a semiconductor channel with a widthW and length L. The semiconductor channel width may be, for example,from about 1 micrometers to about 5 millimeters, with a specific channelwidth being about 5 micrometers to about 1 millimeter. The semiconductorchannel length may be, for example, from about 1 micrometer to about 1millimeter with a more specific channel length being from about 5micrometers to about 100 micrometers.

The source electrode is grounded and a bias voltage of generally, forexample, about 0 volt to about −80 volts is applied to the drainelectrode to collect the charge carriers transported across thesemiconductor channel when a voltage of generally about +20 volts toabout −80 volts is applied to the gate electrode.

Regarding electrical performance characteristics, a semiconductor layerof the present electronic device has a carrier mobility greater than forexample about 10⁻³ cm²/Vs (centimeters²/Volt-second) and a conductivityless than for example about 10⁻⁵ S/cm (Siemens/centimeter). The thinfilm transistors produced by the present process have an on/off ratiogreater than for example about 10³ at 20 degrees C. The phrase on/offratio refers to the ratio of the source-drain current when thetransistor is on to the source-drain current when the transistor is off.

The invention will now be described in detail with respect to specificembodiments thereof, it being understood that these examples areintended to be illustrative only and the invention is not intended to belimited to the materials, conditions, or process parameters recitedherein. All percentages and parts are by weight unless otherwiseindicated. As used herein, room temperature refers to a temperature ofabout 25 degrees C.

EXAMPLE 1 Synthesis of BZP (Compound of Formula (12))

About 5.85 grams of 3,4,9,10-perylenetetracarboxylic dianhydride, 26.77grams of o-phenylene diamine and 7 milliliters of glacial acetic acidwere mixed in a round-bottom flask. The resulting mixture was thenheated with stirring for 8 hours at 210 degrees C., following by coolingto room temperature. A solid product was then obtained by filtering themixture through a sintered glass funnel. Then the solid was washed with1 liter of methanol and slurried with 0.5 liter of 1 percent sodiumhydroxide solution. After filtration again, the solid was washed with600 milliliters of water, and then dried in an oven at 80 degrees C.overnight, yielding 7.5 grams of BZP. The crude product was furtherpurified by sublimation twice for organic TFT use.

Device Fabrication

There was selected a top-contact thin film transistor configuration asschematically illustrated, for example, in FIG. 3. The test device wascomprised of an n-doped silicon wafer with a thermally grown siliconoxide layer of a thickness of about 300 nanometers thereon. The waferfunctioned as the gate electrode while the silicon oxide layer acted asthe gate dielectric and had a capacitance of about 10 nF/cm²(nanofarads/square centimeter). The silicon wafer was first cleaned withisopropanol, oxygen plasma, isopropanol and air dried. Then the cleansubstrates were immersed in a 0.1 M solution of various silane agentssuch as 1,1,1,3,3,3-hexamethyldisilazane (HMDS), octyltrichlorosilane(OTS8), phenylene trichlorosilane (PTS) at 60 degrees C. for 10 min.Subsequently, the wafer was washed with dichloromethane and dried. Thetest semiconductor BZP layer of about 50 nanometers to 100 nanometers inthickness was then deposited on top of the silicon oxide dielectriclayer under a high vacuum of 10⁻⁶ torr. The substrate temperatures wereheld at room temperature, 70 or 120 degrees C. Thereafter, the goldsource and drain electrodes of about 50 nanometers were deposited on topof the semiconductor layer by vacuum deposition through a shadow maskwith various channel lengths and widths, thus creating a series oftransistors of various dimensions.

Device Evaluation

The evaluation of field-effect transistor performance was accomplishedin a black box (that is, a closed box which excluded ambient light) atambient conditions using a Keithley 4200 SCS semiconductorcharacterization system. The carrier mobility, μ, was calculated fromthe data in the saturated regime (gate voltage, V_(G)<source-drainvoltage, V_(SD)) according to equation (1)I _(SD) =C _(i)μ(W/2L) (V _(G) −V _(T))²  (1)

where I_(SD) is the drain current at the saturated regime, W and L are,respectively, the semiconductor channel width and length, Ci is thecapacitance per unit area of the gate dielectric layer, and V_(G) andV_(T) are, respectively, the gate voltage and threshold voltage. V_(T)of the device was determined from the relationship between the squareroot of I_(SD) at the saturated regime and V_(G) of the device byextrapolating the measured data to I_(SD)=0

Another property of field-effect transistor is its current on/off ratio.This is the ratio of the saturation source-drain current at theaccumulation regime to the source-drain current at the depletion regime.After first measurement, device was kept in ambient condition for agingexperiments. TABLE 1 Effect of surface treatment agent on deviceperformance. Surface treatment agent HMDS OTS8 PTS No treatment Mobility6.84 × 10⁻⁴ 3.45 × 10⁻⁴ 3.33 × 10⁻⁴ 7.86 × 10⁻⁵ (cm²/V · s) On/off ratio28000 650000 670 55000 Turn on 6 20 26 22 voltage (V)

TABLE 2 Effect of substrate temperature on device performance. Substratetemperature (° C.) 25 70 120 Mobility (cm²/V · s) 2.28 × 10⁻⁴ 6.84 ×10⁻⁴ 1.28 × 10⁻³ On/off ratio 12000 28000 490000 Turn on voltage (V) 226 12

Transfer characteristics of the devices showed that BZP was a n-typesemiconductor. Table 1 summarizes performance of the device withdifferent surface treatment layers. For these experiments, the substratetemperature was held at 70 degrees C. The device with HMDS treatedsubstrate showed low turn-on voltage, high mobility, and high on/offratio. Although the device with the OTS8 treated substrate exhibitedvery high current on/off ratio, it had a large turn-on voltage and lowermobility. Table 2 summarizes the performance of the devices with HMDStreated substrate at different substrate temperatures. The device withthe substrate at room temperature showed poor performance. While at anelevated temperature such as 70 degrees C. or 120 degrees C. substratetemperature, the device provided a low turn-on voltage, high mobilityand good on/off ratio. Generally, when comparing the transfercharacteristics of devices fabricated on various surfaces and atdifferent substrate temperatures, one can clearly see that the devicewith the HMDS modified surface and a substrate temperature of 120degrees C. provided the best performance.

More important, aging experiments showed that the stability of BZP wasexcellent in air as compared to most other organic TFTs, particularlythose with n-type semiconductors which lose their TFT properties whenexposed to air. A freshly prepared device with HMDS modified wafer assubstrate and substrate temperature of 70 degrees C. showed a fieldeffect mobility of 1.28×10⁻³ cm²/V.s and current on/off ratio about4.9×10⁵. After being exposed to ambient oxygen in the dark for 1 month,a mobility of 5.5×10⁻⁴ cm²/V.s and current on/off ratio about 1.4×10⁵were observed. Only a slight degradation of performance was detected.

EXAMPLE 2 Synthesis of Compound of Formula (19)

About 5.85 grams of 3,4,9,10-perylenetetracarboxylic dianhydride, 18.5grams of 3,4-diaminotoluene and 7 milliliters of glacial acetic acidwere mixed in a round-bottom flask. The resulting mixture was thenheated with stirring for 8 hours at 210 degrees C., following by coolingto room temperature. A solid product was then obtained by filtering themixture through a sintered glass funnel. Then the solid was washed with1 liter of methanol and slurried with 0.5 liter of 1 percent sodiumhydroxide solution. After filtration again, the solid was washed with600 milliliters of water, and then dried in an oven at 80 degrees C.overnight, yielding 7.8 grams of Compound of Formula (19). The crudeproduct was further purified by sublimation twice for organic TFT use.

EXAMPLE 3 (HYPOTHETICAL EXAMPLE) Synthesis of Compound of Formula (8)

About 0.015 mole of 1,4,5,8-naphthalenetetracarboxylic dianhydride, 0.02mole of o-phenylene diamine and 7 milliliters of glacial acetic acid aremixed in a round-bottom flask. The resulting mixture is then heated withstirring for 8 hours at 210 degrees C., followed by cooling to roomtemperature. A solid product is then obtained by filtering the mixturethrough a sintered glass funnel. Then the solid is washed with 1 literof methanol and slurried with 0.5 liter of 1 percent sodium hydroxidesolution. After filtration again, the solid is washed with 600milliliters of water, and then dried in an oven at 80 degrees C.overnight. The crude product is used for next step reaction.

About 0.01 mole of above product, 0.03 mole of 2,3-naphthalene diamineand 7 milliliters of glacial acetic acid are mixed in a round-bottomflask. The resulting mixture is then heated with stirring for 8 hours at210 degrees C., following by cooling to room temperature. A solidproduct is then obtained by filtering the mixture through a sinteredglass funnel. Then the solid is washed with 1 liter of methanol andslurried with 0.5 liter of 1 percent sodium hydroxide solution. Afterfiltration again, the solid is washed with 600 milliliters of water, andthen dried in an oven at 80 degrees C. overnight. The crude product isseparated by column chromatography or vacuum sublimation and yields theCompound of Formula (8).

1. An electronic device comprising a semiconductor layer in contact witha number of electrodes, wherein the semiconductive layer includes acompound wherein either or both of the following geometric isomers ofthe compound are present:

wherein: n is 1, 2 or 3 for the polycyclic moiety; and R₁ and R₂ areindependently selected from the group consisting of a hydrocarbon ringand a heterocyclic group, wherein R₁ and R₂ are the same or differenthydrocarbon ring, the same or different heterocyclic group, or one of R₁and R₂ is the hydrocarbon ring and the other the heterocyclic group. 2.The device of claim 1, wherein the polycyclic moiety is unsubstituted.3. The device of claim 1, wherein the polycyclic moiety is substitutedat least once by a substituent which is a halogen, a hydrocarbon groupor a heteroatom containing group.
 4. The device of claim 3, wherein forthe substituent on the polycyclic moiety, the hydrocarbon group is analkyl group or a phenyl group.
 5. The device of claim 3, wherein for thesubstituent on the polycyclic moiety, the heteroatom containing group isan alkyloxy group, an amino group, a nitro group, or a cyano group. 6.The device of claim 1, wherein R₁ and R₂ are the same or differenthydrocarbon ring.
 7. The device of claim 1, wherein the hydrocarbon ringis a benzo group, a naphthalenediyl group, or an alicyclic hydrocarbongroup.
 8. The device of claim 1, wherein R₁ and R₂ are the same ordifferent heterocyclic group.
 9. The device of claim 1, wherein theheterocyclic group is pyrido, thieno, furo, or pyrro.
 10. The device ofclaim 1, wherein the hydrocarbon ring and the heterocyclic group areunsubstituted.
 11. The device of claim 1, the hydrocarbon ring and theheterocyclic group are substituted at least once with a substituentselected from the group consisting of an alkyl group, an alkyloxy group,a halogen, and a nitrogen containing group.
 12. The device of claim 1,wherein the device is a thin film transistor.
 13. The device of claim 1,wherein both the cis and trans geometric isomers of the compound arepresent.
 14. The device of claim 1, wherein n is 2, R₁ and R₂ are bothan unsubstituted benzo ring, and the polycyclic moiety is unsubstituted,yielding benzimidazole perylenetetracarboxylic acid diimide.
 15. Thedevice of claim 1, further comprising a plastic substrate.
 16. Thedevice of claim 1, the semiconductor layer has a thickness ranging fromabout 10 nanometers to about 1 micrometer.
 17. A thin film transistordevice comprising: an insulating layer; a gate electrode; asemiconductor layer; a source electrode; and a drain electrode, whereinthe insulating layer, the gate electrode, the semiconductor layer, thesource electrode, and the drain electrode are in any sequence as long asthe gate electrode and the semiconductor layer both contact theinsulating layer, and the source electrode and the drain electrode bothcontact the semiconductor layer, wherein the semiconductor layerincludes a compound wherein either or both of the following geometricisomers of the compound are present:

wherein: n is 1, 2 or 3 for the polycyclic moiety; and R₁ and R₂ areindependently selected from the group consisting of a hydrocarbon ringand a heterocyclic group, wherein R₁ and R₂ are the same or differenthydrocarbon ring, the same or different heterocyclic group, or one of R₁and R₂ is the hydrocarbon ring and the other the heterocyclic group. 18.The device of claim 17, wherein the polycyclic moiety is unsubstituted.19. The device of claim 17, wherein the hydrocarbon ring and theheterocyclic group are unsubstituted.
 20. The device of claim 17,wherein n is 2, R₁ and R₂ are both an unsubstituted benzo ring, and thepolycyclic moiety is unsubstituted, yielding benzimidazoleperylenetetracarboxylic acid diimide.
 21. The device of claim 17,further comprising a plastic substrate.
 22. The device of claim 17, thesemiconductor layer has a thickness ranging from about 10 nanometers toabout 1 micrometer.